Experimental studies are being conducted in subhuman primates in which maintained hypertension is being induced through a conditioning regimen of stress. The feasibility of this approach has been previously demonstrated. The aim of these studies is to examine the possible role of adrenergic mechanisms both in peripheral organs and within the central nervous system in the pathogenesis of this form of experimental hypertension. Cardiovascular measurements, during the development of the condition are made with chronically implanted sensors. The role of adrenergic mechanisms is being examined using blood, urine and tissue biochemical and histochemical evaluation of adrenergic amines and especially by determination of amine turnover rates in peripheral organs as well as in the hypothalamus. In addition measurements of plasma renin activity and renin substrate concentration will be made.